Posted
by
samzenpus
on Sunday July 31, 2011 @07:05PM
from the catching-the-waves dept.

judgecorp writes "Everlasting green energy for RF tags and other low-power devices could be possible as scientists have harvested energy from ambient radio waves using cheap antennas printed by an ordinary inkjet. The scientists, from Georgia Tech, started at 100MHz but have now produced systems which scavenge power at up to 60GHz, allowing them to draw power from most of today's major radio technologies."

Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

The radio source is there all the time anyway, It is there for other uses.

But as should be obvious, the vast majority of radio waves are never used, being disparate over vast distances or absorbed by the earth itself. Utilizing this "wasted" energy costs nothing, because we are already emitting that energy, and utilizing it costs no more. At the emitter you can't measure if a radio wave hits one antenna or a million antennas. Its no different to you as the sender of that wave.

So by using freely available wasted energy these devices obviate the need for ANOTHER power source and are therefor green.

I think you mean that marketing has polluted the word so thoroughly that it is hard to take it seriously. In a way it has been gang raped and never truly recovered.

However, the intended meaning of "green" to scientists and intellectuals (I guess) is that the technology results in a net loss of expended energy somewhere. It may be generating energy, or just being more efficient at an unclean process, therefore making it "green" because it is not as bad as the alternative.

You completely missed my point. It's not about bragging rights, or which is more efficient.

The fact is that BOTH the Prius and the Polo Bluemotion are significantly more efficient in fossil fuel use. This leads to:

1) A decreased dependency on Oil.2) Proof that these technologies work and that we have the opportunity to learn from them as they are in use everyday.3) What I also did not mention, was that the Prius, also produces less pollution. I assume the Polo Bluemotion does the same?

Diesel engines will run off a variety of fuels, but you do need a little skill to properly adjust them to differing fuel viscosities, flamabilities, and so on. They come set for 'generic pump diesel.' The modifications are not difficult, but if not done efficiency will be reduced and you might end up belching soot from the exaust. So it's something you'd need to talk to a mechanic about. There are companies that will modify a car for biodiesel operation for a fee. This is also why biodiesel is often sold mi

There were articles in radio magazines decades ago about people living near transmitters harvesting free energy, and the broadcasters maintaining that it was illegal to do so and would interfere with reception. I'm no expert but it seems that if you are converting radio waves into electricity then you are removing some energy from them, meaning that there is less energy available for others to receive. How significant that is I don't know... Say everyone started using this technique, would it affect recepti

So I won't be able to watch TV, listen to the radio, nor use my cellphone when the warehouse next door is filled with RFID tags.

This also is only "everlasting" and "green" for as long as the nuclear power plants are feeding the broadcasters with cheap energy. Unless the antennas can generate enough energy from the cosmic microwave background radiation.

This also is only "everlasting" and "green" for as long as the nuclear power plants are feeding the broadcasters with cheap energy. Unless the antennas can generate enough energy from the cosmic microwave background radiation.

Today, this energy is wasted 100%. If we can harvest a little out of it, it's a bonus.

Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

They do, indeed, consume some energy from the RF broadcast(in principle, if you really chaffed the place with them, the reduction in SNR might actually be noticeable by devices trying to communicate...) However, there are two other considerations:

1. Particularly in classic broadcasting(less your fancy 802.11-draft-whatever-with-beamforming-and-a-line-of-sight-yadda-yadda smart antenna nonsense) a substantial amount of broadcast power just floats away into the aether, never to be snagged by any receiver. So long as you are(by making receivers super cheap) just burning through some of this formerly wasted power, the energy counts as "free". Not until your piggybacking requires the towers to start cranking it up is their a cost.

2. If the deployment of some distributed-sensor net widgetry is an inevitability(there are legimitate grounds for question at this point; but we generally don't take advantage of them) it has to be powered somehow. The major contenders are A. Lithium primary cells: unless somebody plans on cleaning the whole thing up a decade from now, the delightsome battery goo is going straight into the environment. B. Photovoltaics(in suitably sunlit locations that are OK with sporadic power): the energy generation itself is clean, the manufacturing and some of the components are rather less so. C. Piezoelectrics: not all of the suitable candidates contain lead; but a lot of the common ones really ought to be collected after use.

In our brutally entropic universe, nothing is truly "green"; but it is quite possible that RF harvesting will prove to be green-er and/or more convenient in some applications.

99.9998% of the power emitted by my pocket cell phone is wasted. Only the minute fraction of those waves that happen to coincide with the line between myself and the cell tower are actually converted into anything useful. Sadly, the 99.998% ratio is probably optimistic, it's likely to be considerably worse than that!

So here we are, covering the Earth with radio-emitting devices by the billions, (with a "B") with emissions ranging from a few milliwatts per device up into the millions. Thanks to the inverse-s

The "offtopic" is hardly fair, RF-energy harvesting(conveniently combining the signal and the power) found its first major application in early AM radio setups. TFA, though, focuses on advances in antenna design and fabrication that allow much more compact, and far broader-spectrum energy harvesting. The AM antennas of yore, particularly in designs without any amplifiers available, were often not exactly monuments to compactness...

True - I used to have a crystal set that I'd occasionally hook up to a digital analogue clock and it would run fine throughout the day and up until one of the more local stations went off the air for the night.

Think of it this way; how much power is a local radio station transmitting? Maybe, 100 kilowatts? Now, think how much of that signal the cross-section of your antenna is intersecting. Suppose you're a mile away. What percentage of the surface area of a sphere 1 mile in radius does an antenna a few square cm cover?

Area = 4/3PIr^2, right? so, about 4 square miles surface area. A square mile is 4,014,489,600 square inches, so the sphere would be about 16,800,000,000 sq inches. Say the antenna covers

The article mentioned power in the milli and microwatt neighborhood. So I dont think there will be anything like that in the *near* future. However, the article actually seemed a bit sparse when it came explaining the practicle uses. It mentioned a temperature sensor, but what would that sensor do? Would it transmit data? Would it record it? Just "sensing" is mostly useless, no? Admittedly my understanding of this tech is about nil -- but it mentioned charging capacitors with these things. So I gath

I think that the "green" can be understood in comparison to the alternatives. If you don't power these things with radio waves, you have to use something like either batteries or a proper power installation connected to the mains. Either one of those things is likely to use much more resources. However, the fact you can do these installations without batteries will likely lead to many more of them being done. That will only be "green" if each installation saves much more energy than is used in it's prod

It mentioned a temperature sensor, but what would that sensor do? Would it transmit data?

Measure temperature and record it I would assume. If that stuff would get cheap enough you put stickers with it on all food and find out if there after was a lapse in the cooling chain. Reading that info out would then be done with regular RFID gear I assume, as I doubt there is enough power in the air for retransmission.

I also find the concept that this is "green" power a bit off considering just printing these things may take more power than they could give back.

The "green" part is that you might be able to use it in places where you otherwise would need to use a replaceable battery and since it last forever, that can be quite a saving.

There are a number of wireless sensor network technologies whereby the periodically wake a CPU, take a reading, and record it. When full, they then transmit their sensor values to a centralized hub (typically larger and/or solar powered + these) or mesh network. These in turn tend to use this type of technology to steady recharge their batteries. The amount of power recovered is small, but so is the device's power demands. In many cases, people report modest battery life extensions (say something like 20%-3

There are many cool projects out there where you can 'harvest' free wireless energy. I've read about people setting up receivers to pull energy (low wattage of course) from nearby microwave towers and the like. Don't have any sources, but I believe I've heard of some research teams or 'how to get free cheap power' sites/groups being harassed by the folks who owned the towers. All heresy, could not find any sources, anyone know anything else?

Also, and sorry for the cliche attribution, Tesla was a major proponent and researcher in this area, and wasn't a complete kook as revisionist history sometimes paints him to be. Margaret Cheney's "Tesla - A Man Out of Time" is a great read for a comprehensive history covering some of the early research in these areas.

I am not a radio scientist, but... if the new tech pulls power out of the radio signal, isn't this going to a) degrade the signal for anyone 'downstream' of the absorber, and/or force broadcasters to pump MORE power out to maintain signal generally?

It will degrade the signal of downstream recipients. So does absolutely every radio receiver, with no exceptions.However, please consider that the only downstream recipient may well be the earth or space, considering that the path between a transmitter and receiver often does not pass particularly close to another receiver. How much one of these would impact the downstream signal quality anyway depends on just how much power this is extracting, and just how weak the signal would have been at the downstream receiver without this being present.

Also keep in mind that radio waves can be rather fickle. Placing these devices in certain locations may actually increase the received signal strength downstream, perhaps by absorbing an interference source, or by attenuating a secondary path of the signal which would have interfered with the primary signal.

My understanding was that your average conductive thingamajig only absorbed tiny amounts of energy from a passing wave as the electrons shuffled about resulting in a tiny bit of heat, while something designed to take the signal and convert it into power (or even just signal) sucks far more energy out of the signal.

Which reduces the quality of the radio signal for anyone downwave from the power harvesting site. It effectively steals power from the transmitter intended to provide service to those more distant than you from the transmitter.

Permissible is interception for purpose of reception of the signal, such as a crystal radio, at a small scale. Not permissible is powering your lights, robots, or anything else that does not simply turn the signal back into its intended form.

It may be permissible to leech power from a WiFi signal in order to power a device that will use the data in the stream if you could be sure you're stealing power from signals intended for you and no one else.

But AFAIK the rules are to protect man-made signals, unless the scientific community have petitioned to protect their ability to study background radiation by preventing the same harvesting of power from natural radio sources, else they'll have to do their studies elsewhere.

Soâ¦ What about shielding then? Having RF shielding to protect electronics (or using building materials that shield an entire room or house for that matter) also degrades the downstream signal, without using the data in any way.

I could be wrong Ââ" I frequently am â" but I doubt your argument would really hold in practice.

Incorrect. It doesn't reduce the signal quality for anyone downwave from the transmitter. It only reduces signal quality for those in the direct path of travel in a line intersecting the transmitter and this power harvesting antenna. It can only interact with waves that travel directly through it already. It doesn't alter the path of travel of nearby waves to suck them in. In this it is just like any other receiving device, meaning it wouldn't effect signal quality any more than having an equal number of r

Considering the height of radio/TV towers, the direct path of travel is mostly going to be into the ground anyway. The energy this would pick up would be wasted anyway.

This is only true if you're fairly close to the broadcasting antenna. Thanks to the curvature of the earth, what's on the top of a mountain, 50 miles away, is now at ground-level... Any yes, at that range your neighbors on the opposite side are picking up TV signals barely above ground level where you are, if not picking-up on signals that

Which reduces the quality of the radio signal for anyone downwave from the power harvesting site. It effectively steals power from the transmitter intended to provide service to those more distant than you from the transmitter.

Permissible is interception for purpose of reception of the signal, such as a crystal radio, at a small scale. Not permissible is powering your lights, robots, or anything else that does not simply turn the signal back into its intended form.

It may be permissible to leech power from a WiFi signal in order to power a device that will use the data in the stream if you could be sure you're stealing power from signals intended for you and no one else.

But AFAIK the rules are to protect man-made signals, unless the scientific community have petitioned to protect their ability to study background radiation by preventing the same harvesting of power from natural radio sources, else they'll have to do their studies elsewhere.

I remember it was demonstrated that people living close to the grid could get free energy simply by using a coil.

It did not take long though until this became prohibited as it actually did tap the energy from the cables. It even resulted being possible to detect someone was tapping the power.

So here we are again, this time with power from radio waves. How much interference does this cost if we add to the scale? will the radio stations and wireless access points get reduced range by this? If so, don't be sur

> I remember it was demonstrated that people living close to the grid could get free energy simply by using a coil.> It did not take long though until this became prohibited as it actually did tap the energy from the cables. It even resulted being possible to detect someone was tapping the power.

That's actually pretty cool if true. You have any links or google-fu terms to use so we can find out more about this?

I went researching this one time and so far as I can tell, it's a almost a complete urban legend. The version that I heard was that some guy lived directly under some high-voltage power lines. Huge kilovolt transmission lines with gigantic steel towers and a dozen or more conductors. Anyway, the story went that he built a large copper coil in his attic, and managed to leech enough power to light his whole house. The electric company eventually notices that his electricity bill dropped by 90%, the police get

This was from about 1980-85 so it was way before Internet...It was demonstrated with a 60w light bulb, sure it was not as bright as it would have been if connected to the cord, but the coil was for sure no more than a kilo, mostly copper. The light bulb was connected to the coil and it was demonstrated holding it up in the air, I were allowed to hold it up myself. The closer we got by the power lines the brighter the light.

So here we are again, this time with power from radio waves. How much interference does this cost if we add to the scale?

None. No interference is generated by a properly-functioning receiver.

will the radio stations and wireless access points get reduced range by this?

Every antenna, tree, power line, flag pole, chain-link fence, and filing cabinet within range of a transmitter is already shunting a small portion of that transmitter's power to ground. The rest of the signal which is unhindered by any natural

Not to mention there is a difference between a shield 100 feet from a source and 3 miles. Just like a shadow, the affected area is a matter of size and distance. A piece of paper miles miles from a source isn't going to have much of shadow.

It costs an negligible amount of money to produce, and a radio transmitter is already throwing away energy by transmitting in all directions, irrespective of there being a receiver in that direction or not. Am I going to start paying for the radio wave energy being absorbed by my body, too?

Gee, an antenna converts radio waves to AC. This phenomenon has been quite well known since the 19th century.
For something a little more modern, and a whole lot better than a fucking printed antenna, you can use a metal fractal antenna for wide band coverage.

Did you miss the bit in the summary about how this is being done using an antenna printed on paper, using an inkjet to provide a very low cost of production? The 19th century I've read about didn't have inkjet printers or the nano-tech metallic ink to create them.

Do you reject any other advances in approach that "have been done before differently"? Drive a steam powered car (yes, I know they exist), because "converting liquid fuel to motion by burning it to create energy has been quite well known since the

in the 19th century they had pencils that could put graphite on paper, you can draw your very own antenna (or circuit conductors) for less than ten cents of materials. You can make your own conductive ink too. These things have been part of fun science experiments for kids for decades, I did them 35 years ago. Steam engines are thousands of years old, by the way.

Metal antenna can be made cheaper than their silly exotic inks, and are far more durable. For a few bucks, one can make a homemade conductive ink with graphite, fixer and solvent, that's an old kid's experiment from decades ago, can brush that stuff on clothing or paper or a wall and use as antenna or as wires to connect circuit elements. a bit more versatile than this article's ivory tower dweebs and their complicated way of making something less useful, more expensive, less durable....I give this ten

They've re-invented an older model Checkpoint anti-theft tag, the square "sticker" model 410 with an antenna printed in conductive ink and an IC at the center. The Checkpoint tag IC is rather dumb, but then the whole tag costs about $0.05.

The scavenging device could piggy-back solar energy panels so that, when the system stops generating power at sundown, the wireless energy could be used overnight to increase the battery charge or to prevent power leakage. The devices would also be useful in remote areas where an outage of a traditional power source could be flagged by sending a distress signal from an antenna-powered unit.

These are incredibly stupid ideas...

If you're using even the tiniest of solar panels for power, the extra power from th

If you embed 1,000 of these milliWatt antennas in the floor of your house you get 1 W. With a large house you might even be able to get enough energy to power something or charge a battery. You don't degrade signal quality for anybody if you live at the first floor. Governments could even support this method of harvesting wasted energy, especially if the decide to tax it;-)
I wonder what's the power used by a typical radio/TV station. We can't collectively collect more than they collectively emit.

Assuming that 1000 antennas stacked together produce 1000x the output of one antenna. I doubt it and imagine that beyond a certain number you have harvested all there is and hit serious diminishing return.

Why do so many of recent "technology breakthrough" articles follow the same pattern.1. Take an experiment that shows some minor interesting results (in this case the ability to pull microwatts from radio waves)2. Extrapolate it into unproven areas (in this case the ability to pull a milliwatt)3. Combine it with another theoretical, non commercial technology like superconducting motors, lithium air batteries or in this case super-capacitors.4. call it a breakthrough

In my mind it is not a breakthrough until the technology is scaleable and commercially viable. Until then it is interesting science and only that.

The power pulled out of the magic air space comes from somewhere, and is no longer going somewhere else. One power source will not make a difference. Just like one WiFi access point does not crowd out the spectrum. Have you looked around at how many networks you see? As more people use this, it will cast shadows behind it, shortening the range. The person providing service will have to crank up the power to overcome this, or provide serveice to less people.

Alright, so we don't put these devices in walls and on ceilings? I still don't see how these will require the reaction you point out. If these are installed in tiny devices (Like RFID devices.) and carried in pockets or attached to keyfobs, they're going to have NO effect on the interception of radio signals unless you stick a few around your cellphone. These antennas aren't being used to paint walls, cover windows or wrap around your laptop. I think you're completely missing the point of this antenna.

They're going to have NO effect on the interception of radio signals unless you stick a few around your cellphone.

I think you miss the point again. It does impact the reception of radio signals and this energy isn't "free". The proposal here is to be a leech on what somebody else is doing and it will impact the broadcaster.

To note a similar situation, high voltage power lines that connect power plants to major cities also "broadcast" E-M radiation around the towers coming from the transmission of the power itself. Sometimes enterprising individuals living close to these towers can "harness" this energy in several wa

Light going onto solar panels may deprive plants from being able to receive that light. The issue here isn't just one of these devices or doing "experiments" with some ambient radio energy, but what happens when millions or billions of these devices are made and all tapping into that energy. That would be like covering all of the farmland completely with solar panels.... then how will food be grown? One or two of those things in strategic places or placed on rooftops that otherwise don't use that sunligh

Maybe a dumb question, but do RF sinks like this act like 'black holes' for radio waves, affecting the reception quality within a kind-of 'event horizon' vicinity (maybe even requiring more power at the transmitter) ?

I don't think you can measure the effect at the transmitter of generating a wave that was otherwise destined to be absorbed by the surroundings or dissipated into space vs being detected on an antenna.

Perhaps a log floating on a pond into which you throw a rock blocks the ripple and creates a lee, and perhaps a lillypad in that lee bobs less, bit it makes no difference to the stone you throw unless your primary aim was to ripple that particular lillypad.

I suppose you could totally mask the intended receiver (TV aerial) of that TV signal by wrapping it in these paper antennas.But the energy was already expended sending the wave. The transmitter won't need more power if that signal gets absorbed by the buildings or by the paper antenna. The antenna can only capture the energy already impinging upon it from the signal. It can't pull any more from the transmitter.

Well put, but considering the dimensions and distances involved, it would be more like a needle sticking upright in the water shielding the lily pad than a log. The area shielding by the interference would be insignificant and only if it was in direct LOS.

I keep equating it to the story about standing next to a transformer at an electrical substation - or high-power line with a coil, and trying to leach power from it. (I'm botching/simplifying the idea here)

One might argue "I'm not stealing power, because I'm just letting the EM field that the line/substation/coil is already sending through the air - go through my coil).

However, the field's emitter does have to work harder to generate the power which the consumer is using. If this wasn't the case, a powe

I might be wrong (read: I'm talking out my ass here), but two big differences between tapping electrical-line power and tapping radio waves, in this respect, are that first, there is generally a lot more energy siphoned off the power lines, and second, the purpose of radio towers is to emit "x" amount of power with no expectation of ever seeing it again. OTOH, the power lines are being monitored on both ends, and the difference by EMF loss is compensated for by pumping more power into the system. While stri

A real engineer can speak to this better, but there is a big difference between the "near field" where you are actually coupling magnetically/capacitatively with the source and radiation which transmits energy over an arbitrary distance. I believe if you are stealing power by putting a big coil next to a power line you are essentially making half of a transformer and directly drawing power through it... whereas if you are at a greater distance all you can do is intercept radiated energy, which is already g

As has been said above, what happens is that you limit the range of who can receive that signal. It is pretty much is the same thing, just a matter of scale and distance. If a radio signal at a certain power would go 200 miles before it is so weak it can't be used, millions of these devices might make the signal only go 150 miles instead or perhaps less. Do you think that matters to a broadcaster?

Maybe a dumb question, but do RF sinks like this act like 'black holes' for radio waves, affecting the reception quality within a kind-of 'event horizon' vicinity (maybe even requiring more power at the transmitter) ?

Not Really.EM comes in two main flavoursNear Field & Far Field.In the near field you have a good chance of 'loading' the antenna, thus 'robbing' power but you need to be mighty close at high frequencies. eg. Within few cm at 1GHz.In the far field, the EM wave propogates, and you as the reciever have no influence on the transmitter.Do you rob other recievers around you? Yes, but the effect when compared to buildings, trees, the earth would negliable. A propogating wave will also fresnel around you. You w

Think body embedded sensors for instance. They use a tiny amount of power; getting at them for battery replacement is very invasive; and active recharge though an external coil or similar requires external equipment and having users remember to do so would be a common point of failure.

A milliwatt is more than enough (actually at least a 1000 times) to power the power down states of devices I have built myself.If you use it to trickle charge a capacitor, you can even sustain short power on states, if they are rare enough.